The present invention refers to a switch drive for a rotary switch, especially to a switch drive with a switching angle of 90.degree..
A switch drive of the concerned type is known from the U.S. Pat. No. 4,717,799 which includes an input shaft driven by an electromotor and supporting an intermediate part in the form of a gear. The gear meshes with a pinion which carries an eccentric engaging member projecting into a groove of a switch arm to rotate the latter about a switching angle of 90.degree.. The switch arm is fixedly connected to a switch drive shaft to transmit the switching movement thereto. Since the engaging member describes a hypocycloid, a switch drive of this type attains a high switching speed with smooth initiation and smooth termination of the switching action, and simultaneously accomplishes a precise positioning of the switch arm in both its end positions without requiring additional stop members.
Such a switch drive is, however, rather complicated to manufacture and is of considerable dimensions especially when high torques are desired because it requires an electromotor and an additional slipping clutch associated to the latter.